This invention relates to shoe drum brakes provided with an automatic shoe clearance adjusting mechanism.
A typical shoe drum brake means provided with automatic shoe clearance adjusting mechanisms comprises a pair of arcuate shoes, a first strut having a cylindrical portion provided with an open end, a second strut having an external screw thread portion telescopically received in the cylindrical portion of the first strut, an adjusting nut threadingly engaging with the screw thread portion of the second strut and abutting the open end of the cylindrical portion of the first strut, and an automatic shoe clearance mechanism associated with a hand brake lever. The mechanism includes a supporting shaft pivotally connecting one end of either of the first and second struts with the hand brake lever, and means for rotating the adjusting nut in association with the pivotal movement of the hand brake lever thereby adjusting the overall length of the first and second strut. The mechanism and the first and second struts extend between the pair of shoes with one end of the other of first and second struts being connected to one shoe and the mechanism being connected to the other shoe through the hand brake lever.
In the non-actuated condition of the hand brake lever or the shoe clearance adjusting mechanism, an assembly consisting of the first and second strut, the shoe clearance adjusting mechanism and the hand brake lever is floatingly supported in the brake, with the supporting shaft of the shoe clearance adjusting mechanism usually being supported on a backing plate. Therefore, there are problems, due to vibrations or the like, such that mutually engaging parts will wear, thereby reducing the durability of the brake, or a rattling noise will be generated during the running of the vehicle or the like.